Description:
------------
Based upon the documentation in php.ini and documentation [1], I set mail.log in php.ini to the boolean '1', and expected it to send logging output to wherever error_log points to. This caused unexpected errors like "Warning: mail(1): failed to open stream: Permission denied in <script>"

It cost me [2], and others too [3], some time to realize that mail.log expects a path to the logfile it needs to write, and no boolean.

Please, add some more detail to the documentation of the parameter mail.log

[1] http://php.net/manual/en/mail.configuration.php
[2] http://news.php.net/php.general/309710
[3] http://stackoverflow.com/questions/1906403/mail-failed-to-open-stream-permission-denied